Tree Research

Green Streets- Stormwater management system for paved areas

A unique structural soils system is being designed to retain 100% of runoff from a 25-year storm event.The InitiativeDeveloping green infrastructure technologies that protect water quality by reducing contaminants in urban runoff is gaining interest among regulators, developers, and consultants. Research at the USDA Forest Service (Pacific Southwest Research Station’s Center for Urban Forest Research) currently involves quantifying the benefits tree crowns have on runoff reduction. This project builds on existing knowledge by studying how the use of structural soils can enhance the role that trees play in onsite stormwater management.

Study ObjectivesTo develop and evaluate a stormwater management system that directs water to a reservoir of structural soil under pavement. Structural soils are engineered to support vigorous tree growth and reduce root and hardscape conflicts, as well as be load-bearing. Trees are an integral part of the system by first intercepting rainfall to reduce runoff rates, and then removing water from the reservoir with their root systems. Using these engineered soils as runoff treatment and storage sites is a new idea.
Key to the system is its ability to be used in ordinary situations with no additional land area required. All developers and municipalities should be delighted to have a beautiful, compact, shaded parking lot with plenty of parking spaces but no runoff-or a shady broad avenue with arching trees and little or no runoff. These ideals seem impossibly distant from most development today, which provides little space for trees. It is possible to increase space for trees by integrating them into the engineered stormwater management system in ways that minimize conflicts and make efficient use of valuable land.
To read more, visit the USDA Forest Service’s Center for Urban Forest Research (Pacific Southwest Research Station).